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Muscular Dystrophy Australia supports people with any one of more than 60 different neuromuscular
conditions, about half of which are classified as muscular dystrophies. These conditions affect
approximately 1 in every 1000 people.
The muscle conditions can be divided into nine broad categories: their main features are described in
the table below. All of the conditions have in common that they cause muscle weakness which has a
profound effect on people’s lives. However, this is where the similarity ends. Some neuromuscular
conditions are so severe that babies die within the first few years of life, whereas others only affect
people in old age and don’t cause severe disability. Most of the conditions have a genetic cause and
are passed down through families (inherited) but sometimes the genetic change occurs spontaneously
in an individual without a family history of muscle disease. Other conditions are autoimmune or the
cause is unknown or poorly understood.
The source of the muscle weakness within the body differs too. For example, muscular dystrophy is
primarily a disease of muscle, often caused by the lack of an important structural protein and as a
result, the muscles are fragile and easily damaged. In other types of muscular dystrophy such as
facioscapulohumeral muscular dystrophy (FSHD) the genetic change results in the production of a
substance that is toxic to muscle.
For some other neuromuscular conditions the muscle weakness originates in the nerves that control
the muscles. For example, amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA)
affect the motor neurons in the spinal cord. Others, such as Charcot-Marie-Tooth disease affect the
peripheral nerves which carry signals from the spinal cord to the limbs. A structure called the
‘neuromuscular junction’ that connects the nerves to the muscles is affected in some conditions, for
example myasthenia gravis.
Each neuromuscular condition causes a characteristic pattern of muscle weakness: it could be just the
legs or the muscles around the eyes and throat. The most severe conditions affect all the muscles of
the body, including the heart and the muscles used for breathing. In most cases intelligence is not
affected. Some conditions such as myotonic dystrophy affect many parts of the body as well as the
muscles. This results in very diverse care needs depending on the condition and the stage of
progression. Often the management of symptoms is complex requiring input from a wide variety of
health care professionals.
There are no specific treatments for most neuromuscular conditions but considerable research efforts
are working towards developing them and encouragingly, many clinical trials are now starting.
Treatments, such as gene therapy to specifically target the underlying cause are being developed for
some conditions, as well as more generalised treatments which aim to reduce the severity of
symptoms by, for example, boosting muscle regeneration. Read about the research MDA funds.
Table 1: Overview of the diverse types of neuromuscular conditions
Cause
Muscular
dystrophies
Genetic
Source of
weakness
Muscle
Myotonic
disorders
Genetic
Muscle
Spinal
muscular
atrophies
Genetic
Motor
neurons
Inflammatory Unknown
myopathies
Muscle
Neuropathies
Genetic or
autoimmune
Peripheral
nerves
Disorders of
the neuromuscular
junction
Other
conditions
affecting the
nervous
system
Autoimmune
(rare genetic
forms)
Neuromuscular
junction
Unknown or
genetic
Metabolic
diseases of
muscle
Genetic
Motor
neurons or
other parts
of the
nervous
system
Muscle
Other
myopathies
Genetic
Muscle
Comments
There are more than 30 types of muscular
dystrophy and each causes a characteristic pattern
of muscle weakness and wasting. The most
common types are Duchenne muscular dystrophy
and FSHD.
‘Myotonia’ (the inability to relax muscles
following contraction) is a feature of these
conditions in addition to muscle weakness. The
most common type – myotonic dystrophy – affects
many other tissues and organs including the heart,
eyes, digestive and hormonal systems and the
brain.
Motor neuron loss causes generalised muscle
weakness. Divided into four types depending on
severity. Life span rarely exceeds age of two for
the most severe form.
Inflammation in the muscles is a common feature.
Inclusion body myositis is the most common
muscle disease affecting the elderly
Damage to the peripheral nerves causes muscle
weakness and wasting, and some loss of sensation,
in the extremities of the body: the feet, the lower
legs, the hands and the forearms. Most common
form is Charcot-Marie-Tooth disease.
Signals fail to pass from the nerves to the muscles.
The most common type is myasthenia gravis
which is characterised by weakness of muscles of
the eyes, face, neck, throat, limbs and/or trunk.
Amyotrophic lateral sclerosis causes wasting and
weakness of all muscles, with cramps and muscle
twitches common. Survival rarely exceeds five
years after onset. Friedreich's ataxia also falls
within this category.
The lack of an enzyme or mitochondrial
abnormalities impairs energy production in
muscle. Symptoms include muscle weakness and
fatigue and muscle pain and swelling after
exercise.
Wide range of rare genetic conditions mostly
affecting the structure of muscle, examples include
nemaline myopathy, centronuclear myopathy and
central core disease.
A brief description of some muscular dystrophies and related
neuromuscular conditions
Muscular Dystrophies:
BECKER MUSCULAR DYSTROPHY
Age of onset: 2 to 16 years. Symptoms are almost identical to Duchenne yet less severe.
Affects pelvis, upper arms and upper legs. Becker progresses more slowly than Duchenne
and survival runs well into middle age.
CONGENITAL MUSCULAR DYSTROPHY
Age of onset: at birth. Generalised muscle weakness, with possible joint deformities from
shortening of muscles. There are at least 30 different types - many types progress very
slowly; some shorten life span.
DUCHENNE MUSCULAR DYSTROPHY
Age of onset: 2 to 6 years. General muscle weakness and wasting, affecting pelvis, upper
arms and upper legs first. Duchenne progresses slowly, yet eventually involves all voluntary
muscles. A wheelchair is required by about age 8 to 11 years and the condition is severe
enough to shorten life expectancy. With high standards of medical care survival is often into
the 30s.
DISTAL MUSCULAR DYSTROPHY
Age of onset: 40 to 60 years. A group of conditions that cause weakness and wasting of
muscles of the hands, forearms and lower legs. Progresses slowly and rarely leads to total
incapacity.
EMERY-DREIFUSS MUSCULAR DYSTROPHY
Age of onset: childhood to early teens. Weakness and wasting of shoulder, upper arm and
shin muscles. Joint deformities are common. Disease progresses slowly, yet sudden death can
result from cardiac complications.
FACIOSCAPULOHUMERAL MUSCULAR DYSTROPHY
Age of onset: teens to early adulthood. There is also an infantile-onset form. Muscles of the
face, shoulder blades and upper arms are among the most affected but other muscles are
usually affected. Progresses slowly with some periods of rapid deterioration, disease may
span many decades. Most people with the disease have a normal life span
LIMB-GIRDLE MUSCULAR DYSTROPHY
Age of onset: late childhood to middle age. Weakness and wasting, affecting muscles around
the shoulders and hips first. There are more than 20 different subtypes - some progress to loss
of walking ability within a few years and cause serious disability, while others progress very
slowly over many years and cause minimal disability.
OCULOPHARYNGEAL MUSCULAR DYSTROPHY
Age of onset: 40 to 70 years. First affects muscles of the eyelids and throat. Progression is
slow, but weakening of throat muscles causes inability to swallow and mobility can be
affected later on.
Myotonic disorders
MYOTONIC DYSTROPHY
Age of onset: 20 to 40 years. Muscle weakness is accompanied by myotonia (delayed
relaxation of muscles after contraction) and by a variety of symptoms that affect other parts
of the body including the heart, eyes and brain. Muscle weakness affects face, feet, hands and
neck first. Progression is slow, sometimes spanning 50 to 60 years. More severe infantile and
childhood forms also exist.
MYOTONIA CONGENITA
Age of onset: infancy to childhood. Muscle stiffness and difficulty in moving after periods of
rest. With exercise, muscle strength and movement return to normal. Condition causes
discomfort throughout life but is not life-threatening.
PARAMYOTONIA CONGENITA
Age of onset: adulthood. Poor or difficult relaxation of muscle which usually worsens after
repeated use or exercise. Condition causes discomfort throughout life but is not lifethreatening.
Spinal Muscular Atrophies (SMA):
SMA TYPE 1 (INFANTILE PROGRESSIVE)
Age of onset: birth to 6 months. Generalised muscle weakness, weak cry, trouble breathing
swallowing and sucking. Do not reach the developmental milestone of being able to sit up
unassisted. Life span rarely exceeds age of two.
SMA TYPE 2 (INTERMEDIATE)
Age of onset: 7 to 18 months. Weakness in arms, legs and lower torso, often with skeletal
deformities. Children learn to sit unassisted but do not stand or walk independently. Although
respiratory complications are a constant threat, children with type 2 SMA usually live to
young adulthood and many live longer.
SMA TYPE 3 (JUVENILE)
Age of onset: 1 to 15 years. Weakness in leg, hip, shoulder, arm and respiratory muscles.
Children learn to stand and walk but some lose the ability to walk in adolescence, others walk
well into their adult years. Life span is unaffected.
SMA ADULT SPINAL MUSCULAR ATROPHY
Age of onset: 18 to 50 years. Weakness in the tongue, hands or feet which slowly spreads to
other parts of the body. A relatively mild form of spinal muscular atrophy, it has little impact
on life expectancy.
Inflamatory Myopathies:
DERMATOMYOTISIS
Age of onset: childhood to 60 years. Inflammatory condition of the muscles that mostly
affects the shoulders, upper arms, pelvis and thighs. Resulting disability is very variable.
Other symptoms include a muscle pain, rash, fever, malaise and weight loss. Usually
responds to treatment with corticosteroid and other immune suppressing drugs.
POLYMYOSITIS
Age of onset: mostly 30 to 50. Symptoms are similar to dermatomyositis except usually there
is no rash or muscle pain. Disease severity and progression is very variable. More women
than men are affected.
INCLUSION BODY MYOSITIS
Age of onset: over 50. A slowly progressive condition causing weakness primarily in the
quadriceps and forearm muscles. Difficulty with stairs, getting out of a chair and a poor grip
are common problems. Swallowing muscles are sometimes affected. In general patients do
not die of the disease, but most meet with some degree of disability as the disease progresses.
Neuropathies (Diseases of Peripheral Nerve):
CHARCOT-MARIE-TOOTH DISEASE
Age of onset: teens to 20 years (occasionally in childhood or infancy). Damage to the
peripheral nerves causes muscle weakness and wasting, and some loss of sensation, in the
extremities of the body: the feet, the lower legs, the hands and the forearms. There are several
different types of CMT and disease progression varies. Dejerine-Sottas Disease is a severe
form.
HEREDITARY NEUROPATHY WITH LIABILITY TO PRESSURE PALSIES (HNPP)
Age of onset: 20 to 40. Recurrent episodes of numbness, tingling, and/or loss of muscle
function (palsy). An episode can last from several minutes to several months, but recovery is
usually complete. Repeated incidents, however, can cause permanent muscle weakness or
loss of sensation.
GUILLAIN-BARRE SYNDROME
Age of onset: all ages. An autoimmune condition in which the nerves are attacked by the
body’s own immune system causing paralysis, muscular weakness and tingling sensations.
The disorder can be mild, moderate or severe, with life support needed in the worst cases.
Most people spontaneously recover, though some will be left with permanent disabilities.
CHRONIC INFLAMMATORY DEMYELINATING POLYNEUROPATHY (CIPD)
Age of onset: any age but more common in the 5th and 6th decades. An autoimmune
condition which causes slowly progressing weakness and loss of feeling in the legs and arms.
Numbness and tingling usually starts in the feet. Balance may also be affected. Severity
varies widely among individuals. Some may have a bout of CIDP followed by spontaneous
recovery, while others may have many bouts with partial recovery in between relapses. CIPD
is treatable by suppressing the immune system although some individuals are left with some
residual numbness or weakness.
Disorders of the neuromuscular junction:
MYASTHENIA GRAVIS
Age of onset: 30 to 50 years. An autoimmune condition where the junction between the nerve
and muscle is damaged resulting in weakness of muscles of the eyes, face, neck, throat, limbs
and/or trunk. Disease progression varies. Drug therapy and/or removal of thymus gland is
often effective. There is a juvenile onset form of the condition.
CONGENITAL MYASTHENIC SYNDROMES
Age of onset: birth or early childhood. Genetic condition causing problems with the way
messages are transmitted from the nerves to the muscles, causing weakness (myasthenia) and
the muscles tire easily (fatigue). Muscle weakness varies depending on the type of genetic
defect, so impact on mobility ranges from mild to severe.
LAMBERT-EATON SYNDROME
Age of onset: over 40 years. Weakness and fatigue of hip and thigh muscles is common.
Lung tumour is often present. Progression varies with success of drug therapy and treatment
of any malignancy.
Other conditions affecting the nervous system
AMYOTROPHIC LATERAL SCLEROSIS (ALS/MOTOR NEURONE DISEASE/LOU
GEHRIG’S DISEASE)
Age of onset: 35 to 65 years. Motor neurons (nerve cells that control muscle cells) are
gradually lost. Wasting and weakness of all body muscles, with cramps and muscle twitches
common. Progressive, ALS first affects legs, arms and/or throat muscles. Survival rarely
exceeds five years after onset.
FRIEDREICH'S ATAXIA
Age of onset: 4 to 16 years. Inherited disease of the nervous system resulting in impairment
of limb coordination, muscle weakness and loss of sensation. Severity and progression of
disorder vary. Often associated with diabetes and heart disease.
Metabolic Diseases of the Muscle:
ACID MALTASE DEFICIENCY (Type II Glycogen storage disease, Pompe’s
disease)
Age of onset: Infancy to adulthood. For infants, disease is generalised and severe with heart,
liver and tongue enlargement common. Adult form involves weakness of mid-body and
respiratory muscles. Progression varies. Enzyme replacement therapy is available.
CARNITINE DEFICIENCY
Age of onset: Early childhood. Varied weakness of shoulder, hip, face and neck muscles.
Often a secondary metabolic condition, progression varies and carnitine supplementation can
be effective.
CARNITINE PALMITYL TRANSFERASE DEFICIENCY
Age of onset: young adulthood. Inability to sustain moderate prolonged exercise. Prolonged
exercise and/or fasting can cause severe muscle damage with urine discoloration and kidney
damage.
DEBRANCHER ENZYME DEFICIENCY (Type III Glycogen storage disease, Cori’s
disease)
Age of onset: 1 year. General muscle weakness, poor muscle control and an enlarged liver
with low blood sugar. Slow progression. Some patients do not experience muscular weakness
until late teens or early adulthood.
LACTATE DEHYDROGENASE DEFICIENCY
Age of onset: childhood to adolescence. Intolerance of intense exercise with muscle damage
and urine discoloration possible following strenuous physical activity. Severity of disorder
varies and intense exercise should be avoided.
MITOCHONDRIAL MYOPATHY
Age of onset: birth to adulthood. Severe muscle weakness, flaccid neck muscles and inability
to walk. Brain is often involved, with seizures, deafness, loss of balance and vision, and
retardation common. Progression and severity vary.
MYOADENYLATE DEAMINASE DEFICIENCY
Age of onset: early adulthood to middle age. Muscle fatigue and weakness during and after
exertion, with muscle soreness or cramping. Patients are often unable to attain previous
performance levels yet condition is non-debilitating and non-progressive.
PHOSPHORYLASE DEFICIENCY (Type V glycogen storage disease, McArdle
disease)
Age of onset: Adolescence. Low tolerance for exercise, with cramps often occurring after
exercise. Intense exercise can cause muscle damage and possible damage to kidneys.
Reducing strenuous exercise can lessen severity.
PHOSPHOFRUCTOKINASE DEFICIENCY (Type VII glycogen storage disease)
Age of onset: Childhood. Muscle fatigue which upon exercise can lead to severe cramps,
nausea, vomiting, muscle damage and discoloration of urine. Disease varies widely in
severity and progression.
PHOSPHOGLYCERATE KINASE DEFICIENCY
Age of onset: Childhood to adulthood. Muscular pain, cramps, muscle damage and urine
discoloration possible following intense exercise of brief duration. Severity varies and intense
exercise should be avoided.
Other Myopathies:
BETHLEM MYOPATHY
Age of onset: birth through to adulthood. Considered a type of congenital muscular
dystrophy. In childhood the symptoms can be hypotonia (floppiness), muscle weakness,
delayed motor milestones, talipes (clubfoot), torticollis (stiff neck) and contractures
(tightness) in the ankles, hips, knees and elbows. The main symptoms in adults include tight
tendons at the back of their ankles, as well as tightness of various other joints especially in
the hands and mild muscle weakness.
CENTRAL CORE DISEASE
Age of onset: at birth or early infancy. Motor skill milestones are reached very slowly and hip
displacement is not uncommon. Condition is disabling but not life-threatening.
CONGENITAL FIBRE TYPE DISPROPORTION
Age of onset: at birth or before age of 1. A rare type of myopathy characterized by hypotonia
and mild to severe generalized muscle weakness.
FIBRODYSPLASIA OSSIFICANS PROGRESSIVA (FOP)
Age of onset: early childhood. An extremely rare disorder where a person's muscle and
connective tissues, such as ligaments and tendons, are slowly replaced by bone. Starts in the
person's shoulders and neck, progressing along their back, trunk, and limbs.
HYPER/HYPO THYROID MYOPATHY Age of onset: childhood to adulthood. Muscle disease caused by under or overproduction of
thyroid hormones from the thyroid gland. Weakness in upper arm and upper leg muscles with
some evidence of wasting. Severity depends on success in treating underlying thyroid
condition.
MINICORE (MULTICORE) MYOPATHY (multi -minicore disease)
Age of onset: infancy or childhood. Rare myopathy with variable degrees of muscle
weakness and wasting. There are different subtypes each with varying symptoms and
severity. Most common type is characterized by spinal rigidity, early scoliosis and respiratory
impairment. Other types may involve the muscle around the eyes, distal weakness and
wasting or weakness around the hips. Weakness is static or only slowly progressive
MYOTUBULAR (CENTRONUCLEAR) MYOPATHY
Age of onset: birth to early adulthood. There are three different types. In the most severe
form babies are born floppy with breathing difficulties and the bones of their head are
malformed. The most common type only affects males. More mildly affected people are often
able to walk well into adulthood but do find themselves in a wheelchair in later life.
NEMALINE MYOPATHY Age of onset: at birth or early infancy. Hypotonia (poor muscle tone or floppiness) and
weakness of arm, leg, trunk, face and throat muscles. In severe cases, children have marked
respiratory weakness. Children rarely survive more than a few years, yet some live into teens.
PERIODIC PARALYSIS - HYPOKALEMIC - HYPERKALEMIC Age of onset: infancy to 30 years. Severe generalised weakness of legs and other muscle
groups with periods of paralysis affecting arms, legs and neck. Severity varies by age of onset
and success of drug therapy.
If you have any questions, please contact us:
Email: [email protected]
Phone: +61 3 9320 9555
Updated 11 August 2014
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